Increased Strength - I feel this one’s close to useless, and a Legendary rarity? Pshah. Make it Common or Uncommon.
Reflex Enhancer - I rarely use it, so I can’t comment. I have won a few close gunfights with it because I got to reload before the enemy, but I use other AM’s so much more.
Auto-Medic - I’ll often use this in Firefight.
Upgraded Shields - Same with the above. I’ll also pair it with the SPNKr Prime or Jorge’s Chaingun at times. Taking a direct hit to the face from an ONI Guass 'Hog and not dying was quite an experience. (To clarify, I was wielding the Prime at the moment)
Patrol Case - Allegedly, this will let you snag extra ammo from power weapons if you call in the same weapon twice… But I don’t actually see this. If I call in an Arclight after emptying it, it refills with the same amount it would have had. Does it not work if your weapon is empty? It’s pretty good to pair up with the Extended Mag weapons though.
Upgraded Thrusters - I don’t often use, but as others have pointed out it can be pretty powerful.
Frag Expert - Pointless.
Splinter Expert - Fantastic in WZ Assault
Plasma Expert - Why is this an Ultra Rare again?
Grenadier - Also great in WZ Assault, or if you expect to be spamming grenades a lot when rushing armories in regular WZ.
Speed Booster - Love this, especially when lugging around turrets or pairing with weapons that grant speed (Whispered Truth, a Prime…). IMO Increased Strength should negate the movement penalty when carrying turrets, but that’s just me.
Wheelman - Essential if you’re going to be using vehicles. Especially rare ones.
Death From Above - Never used it, so can’t comment.
Advanced Sensors - Saving the best for last, why this is a mere “Common” leaves me dumbfounded. It lets you keep an eye on your motion tracker while scoped (great when sniping or sneaking with a Bane), and you can walk around without showing up on radar instead of having to crouch-walk all the time. I love this mod, and it’s way powerful for its rarity level.
I like mixing up the armor mods from time to time, though lately I spend most of my time with Advanced Sensors. For the most part they’ve all got their uses and it depends on your playstyle and what situation you’re in, but I feel that Increased Strength isn’t carrying enough weight to be valued at Legendary, Frag Expert is just kind of meh, and Plasma Expert… Well, I’m not sure. Since you only get one, it doesn’t seem all that useful compared to the other armor mods. Especially since unlike frags, you won’t be seeing many splinters and plasmas around on the map.